I don't know which is correct. It's possible that both are, because of differences in how they are used.
Created https://issues.apache.org/jira/browse/CASSANDRA-2597 to look into this. On Sat, Apr 2, 2011 at 7:12 AM, pprun <pzgyu...@gmail.com> wrote: > Hi Cassandra DEVs, > > I just found there are two implementations of 'cumulative distribution > function' for Exponential Distribution and there are inconsistent : > > *FailureDetector* > org.apache.cassandra.gms.ArrivalWindow.p(double) > double p(double t) > { > double mean = mean(); > double exponent = (-1)*(t)/mean; > return *Math.pow(Math.E, exponent)*; > } > > *DynamicEndpointSnitch* > org.apache.cassandra.locator.AdaptiveLatencyTracker.p(double) > double p(double t) > { > double mean = mean(); > double exponent = (-1) * (t) / mean; > return *1 - Math.pow( Math.E, exponent);* > } > > According to the Exponential Distribution cumulative distribution function > definition<http://en.wikipedia.org/wiki/Exponential_distribution#Cumulative_distribution_function>, > the later one is clear, however, > Could you please explain a bit for the implementation of FailureDetector? > > Thanks*, > *pzgyuanf* > * > -- Jonathan Ellis Project Chair, Apache Cassandra co-founder of DataStax, the source for professional Cassandra support http://www.datastax.com
